The present invention relates to a vehicle seat, and more particularly relates to a vehicle seat for use in a vehicle such as a motor car or automobile.
It is well known that if a motor vehicle is involved in a frontal impact, it is desirable that an occupant of the vehicle should be prevented from moving forwardly relative to the vehicle as the vehicle decelerates. It has been proposed, therefore, to provide a safety-belt in a vehicle which incorporates a lap belt which engages the hip bone of the occupant of the vehicle and, in the event that a front impact should occur, prevents the occupant of the vehicle from moving forwardly by any substantial distance relative to the seat.
It has been found, however, that there may be a tendency for an occupant of the seat to slide under the lap belt, when the vehicle decelerates, with a movement that is sometimes termed xe2x80x9csubmariningxe2x80x9d. This is undesirable.
Various solutions to the problem of xe2x80x9csubmariningxe2x80x9d have been proposed. It has been suggested that a rigid barrier should be provided extending transversely in the front part of the seat squab. The lower part of the pelvis, or the ischial tuberosities, of the occupant of the seat will engage the rigid barrier if the occupant of the seat starts a xe2x80x9csubmariningxe2x80x9d movement. It is, however, undesirable to have a rigid barrier in the front part of a seat squab, since this may give rise to blood circulation problems in the legs of an occupant of the seat. Alternatively it has been proposed, see GB-A-2,332,844, to provide an inflatable air-bag in the front part of the seat squab adapted to be inflated in the event of a frontal impact to restrict any xe2x80x9csubmariningxe2x80x9d motion of the occupant of the seat.
A motion restricting device of this type should act on the front lower part of the pelvis, which can withstand relatively high forces. However, the available surface area presented by the pelvis in this region is very small. Thus the contact surface of the bag should be very stiff, or bag pressure should be very high, for example, of the order of 3 to 5 bars. A textile air-bag can normally only withstand a pressure of less than 2 bars, and the surface of such an air-bag is not stiff. Thus, an air-bag of the type shown in GB-A-2,332,884 does not provide the desired effect in practice.
The present invention seeks to provide an improved vehicle seat.
According to this invention there is provided a vehicle seat, the seat comprising a back-rest and a squab, the squab being provided with a chamber defined by walls of metal, at least part of one wall being constituted by a plastically deformable sheet metal, the chamber being partly bounded by or supported by part of a rigid frame constituting part of the structure of the squab of the seat, the chamber being associated with gas generator means adapted to inflate the chamber, with an associated plastic deformation of said sheet, in response to a signal from a detector.
Preferably the chamber is located substantially centrally of the squab of the seat in a lateral direction.
Conveniently part of the chamber is bounded by part of the frame structure of the squab of the seat.
Advantageously the part of the frame structure of the squab of the seat bounding or supporting the chamber defines a plane termed the supporting plane, a line normal to the supporting plane being at an angle of between 30 and 70xc2x0 to the vertical.
Preferably a line between the centre of the chamber and the H-point of the seat, that is the theoretical average position of the hip of an occupant of the seat, at an angle relative to the normal to the supporting plane at the centre of the chamber of xc2x120xc2x0.
Conveniently the chamber is on a laterally extending beam located in the forward part of the squab constituting part of the rigid frame structure of the squab of the seat.
Preferably the gas generator comprises a pyrotechnic gas generator located within the chamber.
Advantageously the chamber is provided with one or more vent holes.
Preferably the or each vent hole passes through the part of the rigid frame structure of the seat squab bounding or supporting the chamber.
Advantageously the or each vent hole is initially closed by a rupturable foil.
Conveniently the seat squab has a foam layer above the chamber and the rest of the frame structure.
Preferably at least part of the plastically deformable sheet is corrugated.
Conveniently at least a central part of the plastically deformable sheet is reinforced.
In one embodiment the chamber is bounded by a single sheet of plastically deformable sheet metal which is secured to said rigid frame to define the chamber.
Conveniently the gas generator is on the exterior of the chamber.
In another embodiment the chamber is defined by two adjacent metal sheets, adjacent overlying edge regions of the sheets being joined by rolling or folding the edges inwardly towards the centre of the chamber by at least substantially 180xc2x0.
Preferably the edge of one sheet is initially folded by substantially 180xc2x0 about the edge of the other sheet, said one sheet thus being folded by at least substantially 360xc2x0, and the other sheet being folded by at least substantially 180xc2x0.
Conveniently the gas generator is within the chamber.